In a battery which may be used in a cold area like a battery mounted on an electric vehicle, a battery electrolyte may be frozen during non-use.
When the temperature of the battery is lowered, an available input and output electric power of the battery is lowered by an increase of an internal resistance although a state of charge SOC is not lowered. The available input and output electric power finally becomes 0 when the battery electrolyte is frozen. The electric vehicle which uses the battery as an energy source for running cannot run.
Accordingly, there is needed a battery temperature control device configured to control the temperature by warming the battery by a heater before the temperature is lowered to be a state in which this inconvenience of the available input and output electric power is caused.
Conventionally, there has been proposed a battery temperature control device which is arranged to control the temperature by warming the battery by the heater in this way, and which is described, for example, in a patent document 1.
The battery temperature control device of this proposed art performs the temperature control of an in-vehicle battery. The battery is warmed by the heater when the outside air temperature is lowered than a lowest temperature in an OFF state of an ignition switch.